Strut-type suspension is well known in motor vehicles wherein a telescope strut normally incorporating an hydraulic damper is used as one locating member for a motor vehicle wheel. The most common form of strut suspension is the so-called McPherson strut where the suspension spring is located concentrically around the telescopic strut which has an upper mounting point to the vehicle chassis in a tower located above its front wheel arch and protruding into the engine bay of the motor vehicle. The lower end of the strut is typically further located by a transverse link and a fore and aft or drag link.
The wheel alignment of a motor vehicle, particularly the front wheel alignment is important to the safe handling of the vehicle and to prevent wear on the tires. During the life of a vehicle it may be necessary or desirable to adjust the caster and/or camber of a motor vehicle wheel either due to normal wear and tear or to some form of minor damage such as the striking of curbs or other obstacles. On many motor vehicles fitted with McPherson strut suspension, this adjustment is often difficult to perform as the motor vehicle manufacturer provides little or no mechanism for relocating the upper end of the strut where it mounts into the vehicle chassis. It is often necessary to relocate the mounting point of the upper end of the strut to achieve the desired caster and/or camber settings.
It is common for the upper end of a McPherson strut to be secured to the chassis member by way of three vertical studs located on a pitch circle and passing from a flange and bush at the upper end of the strut through aligned holes in the vehicle chassis member. Some manufacturers have provided a degree of adjustment by locating the axis of the strut off-centre from the pitch circle of the studs so that disengaging the studs from the holes in the vehicle chassis member, locating the strut and re-engaging the studs through the holes will relocate the axis of the strut relative to the vehicle chassis member. This is, however, an extremely coarse adjustment which only permits the top end of the strut to be located in three defined positions. Furthermore, if it is required to alter the camber of the suspension without affecting the caster, or vice versa, this adjustment is not possible using the mounting described above.
Another type of vehicle strut type suspension with alignment adjustment is disclosed in U.S. Pat. No. 4,372,575 (Hyma). This patent discloses a mounting apparatus for attaching the upper and of the strut to a stamped sheet metal tower portion of the vehicle superstructure and having provision for adjustment of either wheel caster or wheel camber via the relative movement of the upper and of the strut relative to the towers. In this arrangement the amount of adjustable movement of the mounting apparatus is not sufficient as a series of threaded studs which project from a lower reinforcing member are restricted in movement through slots located within plate members of the mounting assembly. The size and orientation of the slots restrict the amount of possible adjustment.
International Patent Publication No. W093/00244 (McIntyre) discloses an adjustable mount to the upper end of a vehicle suspension strut with adjustability by providing a bush adapted to receive the upper end of a strut, wherein a flange extends radially outwardly from the upper part of the bush. The flange is adapted to be slidable between the vehicle chassis member and a lower clamping plate. A plurality of studs extend upwardly through apertures within the circumference of the flange which are significantly larger than the diameter of the studs. This adjustable mount also suffers from relatively restricted adjustment because the movement of the flange is limited by the size of the apertures through which the studs extend. Whilst such an adjustable mount is able to allow for the alteration of the camber of the suspension without affecting the caster (or vice versa), there is a limitation in providing adequate, adjustability for both the camber and caster simultaneously and for providing sufficient adjustment for negative camber where it is required.